Fuel Milage

[tweiss3]

Don't laugh, the FC is better than the truck on milage.

However, I use fuel milage as a huge indicator for determining if something has gone wrong quick. The cold has killed milage (happens every year on all cars) and its down to about 14.7-15.5 mpg. This is mostly highway and some city mixed in. The question I have is, is that normal? I know edmunds lists 18 highway for NA's but 15?

Anything I can do to improve this (i know :spam: me) but i have adjusted my driving style for rotary (keeping it above 2500 with any throttle over 5%) and do 3k oil changes, checking oil every other fill up (about every 6 days).

[My5ABaby]

When I tracked my mileage I was getting about 23-24 highway and 14 city, averaging around 17.5 for me with mixed.

[MmSadda]

I dunno, that DOES seem pretty low... I usually get gas mileage that low when I thrash on it. I'm running a pretty much stock s4 n/a, with a cat-less exhaust. Shortly after a rebuild I saw as high as about 27-28mpg, pure highway miles. I swapped to a different intake and now see low-mid 20s (likely because the AFM doesn't sit perfectly flat anymore; I need to fix that) and a bit under 20 on a normal tank of gas with a mix of freeway, around down, and hard driving mixed in.

[tweiss3]

Hmmm. Its a stock S5 NA. Magnaflow cat, rebuilt air pump, corksport 2.5" catback with silencer installed, and a cone filter intake. I was up about 18 before the cold weather set in. Could it be the emissions bullshit?

[Rotary Evolution]

sounds about average to me, the rotary really suffers in town for gas mileage so if you are doing more in town that highway it will drop like a rock.

my TII with a fairly aggressive fuel mileage tune gets 24mpg highway but about 13 in town(probably due to my lead foot..). my F-250 4X4 almost trumps it in town. granted it has a fairly large turbo(capable of 600WHP) to spool up so that hurts it more in the stop and go traffic than an n/a does.

[tweiss3]

Hmm, I haven't had it on a highway trip yet, maybe I will find out how well it does soon enough.

[Pete_89T2]

Another factor to consider with mileage, besides the mix of highway/city driving is the length of each of your trips (i.e., run time). If a large percentage of your trips were made doing short runs (city or hwy driving), where you spent most of your time getting up to operating temps, it will drag your average mileage down.

[tweiss3]

I always start my car, let it run for 15 minutes till its warm before beginning my trip. Also, its always about a 30 minute drive, close to 25 miles each way. If that helps determine my driving habit.

[RETed]

I assume you're talking about your location "Akron, Ohio"?
I assume that you're running that OXYGENATED gas crap?
If so, that explains it.
Oxygenated gas will kill, on average, 5% - 10% of your mileage.
The oxygenated additive displaces gasoline, so it takes more of this crap to power the engine.
Oxygenated gas is a @#%*(_%_ conspiracy.

Non-turbo FC's should easily do 15mpg.
Mix in some highway / freeway driving, and it should start to head towards 20mpg.
Start doing some serious freeway driving, and you can easily break 20mpg and start heading towards 25mpg.

At best mileage driving conditions, it'll get close to 30mpg...
To do this, do all your driving in top gear and at 3,500RPM - the key is the RPM's, cause you want to keep it right under the secondary fuel injector crossover point.


-Ted

[Rotary Evolution]

I always start my car, let it run for 15 minutes till its warm before beginning my trip. Also, its always about a 30 minute drive, close to 25 miles each way. If that helps determine my driving habit.

it tells me you like to waste gas. i start my car and boost it to 15psi within a few minutes at times, most of the time it's very rare that i let it warm up more than 30 seconds before driving off. ;)

[tweiss3]

I assume you're talking about your location "Akron, Ohio"?
I assume that you're running that OXYGENATED gas crap?
If so, that explains it.
Oxygenated gas will kill, on average, 5% - 10% of your mileage.
The oxygenated additive displaces gasoline, so it takes more of this crap to power the engine.
Oxygenated gas is a @#%*(_%_ conspiracy.

Non-turbo FC's should easily do 15mpg.
Mix in some highway / freeway driving, and it should start to head towards 20mpg.
Start doing some serious freeway driving, and you can easily break 20mpg and start heading towards 25mpg.

At best mileage driving conditions, it'll get close to 30mpg...
To do this, do all your driving in top gear and at 3,500RPM - the key is the RPM's, cause you want to keep it right under the secondary fuel injector crossover point.


-Ted

Yes, we don't have real pure gas here, fucking tards.

Also this makes complete sense. 3500rpms in 5th gear is quite quick, too quick for being legal around here (fucking 65 max state limit). I may end up trying to see if I can break 20 this summer. Before the cold set in, I was getting 16 pretty easily, and defiantly not taking it easy.

So, my car "should" be in good operating order based on fuel usage. I just need to:
1) stay out of the city all together
2) run real gasoline (fuck this shitty winter mix)
3) stay in a warm area
4) drive faster, but stay in the primary injector range.

[infernosg]

Not much warmer down here in Cinci and I average about 18 mpg (75% city, 25% highway) although it doesn't get driven too much in the winter. I've seen 25+ mpg at least once during a trip to and from Akron. I agree with Rotary Evolution above, there's no need to let your car idle for 15 minutes before going anywhere. From what I read these cars idle at relatively rich air-fuel mixtures. I usually wait about 1 minute before going anywhere (longer if it hasn't been driven in a while) and then just keep the engine speeds lower until it's fully warmed up.

[Pete_89T2]

I always start my car, let it run for 15 minutes till its warm before beginning my trip. Also, its always about a 30 minute drive, close to 25 miles each way. If that helps determine my driving habit.

That would explain the lower than average MPGs. In terms of your run time, for each of your average trips, your car is running for a total of 45 minutes or so, with 15 minutes or so spent idling. Idle = 0 MPG, and if ~33% of your run time is spent at idle, it's easy to see how this would effect your average MPG. Skip the warm up time idling - just drive off but don't beat on it until it's up to operating temp.

[Ender]

My TurboII seems to hover around 18mpg most of the time with mixed driving, and I rarely have a trip that I don't wind it up hard at least a couple times. I have gotten 25mpg before, but it was straight from a gas station to the interstate with a tailwind to the next gas station like 300 miles later. I don't think I've seen over 20mpg more than a couple times in three years. I would think an NA should have no real trouble doing this though.

[tweiss3]

I'll try the minimal start up times, and hope for warm weather to see if I can easily get 18.

[NoDOHC]

My record mileage stock ('86 6-port N/a) was 31.2 mpg. This was driving through Ohio Westbound on a 95 degree day at 85 mph (that is how fast the traffic was going). At 85, I was turning about 3200 rpm (which backs up Ted's theory).

We should have a sticky on here somewhere for mileage tips:
Don't lug below 1,500 rpm.
Don't rev past 3,800 rpm (as Ted said, try to leave a little margin here).
Do not move the throttle any more than necessary.
Try to keep speed above 60 mph.
Advance timing 10 degrees or so.
Remove power steering belt for long trips.
Keep new spark plugs.

This should get you into the mid 20's consistently. My '91 with power steering connected Automatic trans, etc, will give 28 mpg highway (more like 21 city).

[My5ABaby]

We should have a sticky on here somewhere for mileage tips:
Don't lug below 1,500 rpm.
Don't rev past 3,800 rpm (as Ted said, try to leave a little margin here).
Do not move the throttle any more than necessary.
Try to keep speed above 60 mph.
Advance timing 10 degrees or so.
Remove power steering belt for long trips.
Keep new spark plugs.
Buy a Geo Metro

Fixed.

[tweiss3]

Lmao, I can deal with the shitty milage, that's not too much of an issue (other than the 100+ bucks in fuel a week) but this thread was more or less determining if my milage was about normal.

I honestly believe consistantly tracking or checking your fuel milage is one of the best ways to find out early if something is going wrong with your drivetrain.

[RETed]

I agree.
This is why I track all my cars mileage just to get a hint something is wrong.
The way I do it, which makes it easiest for me, is to just run 10 gallons per fill-up.
Calculating MPG is easy! :)

My '87 Turbo does a consistent 12.5mpg now.
This is basically all city driving, as work is only 4 miles away for me.
When I jump on freeway, it'll hit 20mpg pretty easily.
Ported 13BT, hybrid turbo, Haltech E8, Crane Cams HI-6 on leadings

My best record has been a Sacramento, CA to Las Vegas, NV run...
400 miles between fill-up's
~13 gallons per fill-up, due to smaller S4 gas tank (16.6 gallon max)
That nails exactly 30mpg.
All freeway / highway, keep tach under 3,800RPM, average speed around 80mph
Car back then was running reprogrammed ECU, small hybrid turbo, Crane Cams HI-6 on leadings, same ported 13BT motor.


-Ted

[Ender]

When I was still a car n00b (14yo) my Mazda 323 dropped suddenly from ~28mpg to about 14 :lol: and had no power (like it had any to begin with). A couple days later the damn timing belt broke trying to start the car, the tensioner pulley had seized! Now if my RX-7's mileage drops it probably means the stupid wastegate is broken open again :(

[sv51macross]

Another factor to consider with mileage, besides the mix of highway/city driving is the length of each of your trips (i.e., run time). If a large percentage of your trips were made doing short runs (city or hwy driving), where you spent most of your time getting up to operating temps, it will drag your average mileage down.

Hmm...I'm averaging 11-12mpg with Lucy. No O2, possibly bad thermo, and rusty BAV/IAC. Mostly trips back and forth to class. The college is 10 mins away and it's almost all 'city'. I keep RPM between 2 and 3 thousand. Nowdays I just let her idle a couple minutes to warm the oil and go.

Guess I know why my mileage is so bad.

[Ender]

The lack of an Oxygen sensor is probably KILLING your mileage. The ECU can't know if it's running rich or lean, so it will default to running very rich just in case. Install one and report back with how much it improved.

[tweiss3]

Ive worked on driving habits and am up to 16.2 without any change of areas driving. Also im not taking it easier, just being more aware of gear choice and cruising rpms.

[Jims5543]

Hmmm...

13B-REW swapped.

475 RWHP.

1300/870 injectors.

Motec M4 tuned for cruising keeping the AF ration in the 14.1 range at 80 MPH.

MPG - 21 on the highway
- 17 around town
- 10 when I am not being nice and trying to get arrested
- 5 on the track

[Ender]

Drove from Iowa to Kansas and back this weekend. Cruised about 82mph 90% of the way there and got 19mpg. Majority of the way back I was driving ~73mph and got 23mpg. Both ways, naturally, had at least a few quick sprints.